Protector circuit for cardiac apparatus

ABSTRACT

A protector circuit having relay arrangement and gas discharge tubes coupled between first electrodes attached to a patient and the amplifier of an electrocardiograph, the relays comprising fast acting reed relays which break the circuit when a defibrillator is energized to apply a countershock voltage across second electrodes mounted on said patient, to prevent the countershock voltage from distorting the heartbeat waveform produced by the electrocardiograph. The gas discharge tubes prevent voltages in excess of a predetermined value from reaching the amplifier by conducting such voltages to ground, whether the relays are opened or closed.

United. States Patent 15] 3,653,387 Ceier [4 1 Apr. 4, 1972 154]PROTECTOR CIRCUIT FOR CARDIAC 3,236,239 2/1966 Berkovils ..12s/419APPARATUS 3,442,269 5/1969 Druz ..128/419 D UX [72] lnventor: Richard R.Ceier, East Aurora, N.Y. FOREIGN PATENTS OR APPLICATIONS 73 Assigneez.Cardiac Electronics, Inc., Clarence, N.Y. 850,926 9/1952 Germany [221'Filed: May 1970 Primary Examiner-Anton O. Oechsle [21] APP] 33,172Attorney-Sommer, Weber and Gastel A Related US. Application Data [57]ABSTRACT [63] Continuation of Ser. No. 653,201, July 13, 1967, Aprotector circuit having relay arrangement and gas b d d, 1 dischargetubes coupled between first electrodes attached to a I patient and theamplifier of an electrocardiograph, the relays s2 u.s.c1, ..'.12s/2.06R, 128/419 D comprising fast wing reed relays which break the circuit 511 Int. Cl. ..A6lb 5 04 when a defibrillator is energized to pp y acoumershock volt- [58] Field oiSearch ..12s/2.05 R, 2.06,4l9D age mossSecond electrodes mounted on Said Patient, to

prevent the countcrshock voltage from distorting the heart- [56]References Cited beat waveform produced by the electrocardiograph. Thegas discharge tubes prevent voltages in excess of a predetermined UNITEDSTATES PATENTS value from reaching the amplifier by conducting suchvoltages to ground, whether the relays are opened or closed. 3,527,2289/1970 McLaughlin ..l28/419 D 2,673,559 3/1954 Fawcett ..128/2.06

3 Claims, 1 Drawing Figure g SCHMITT' 15$: INDICATINQ 4| MULTIVIBRATORDEV'CE I I I I I I I I I I I I I I I I I I I I I I I I I I I IHORIZONTAL SWEEP AMPLIFIER INVENTOR.

DEVICE- INDICATINGI IER SINGLE S H O T MULTIVIBRATOR SCHMITT TRIGGERPatented April 4, 1972 1 PROTECTOR CIRCUIT FOR CARDIAC APPARATUS Thepresent application is a continuation of application, Ser. No. 653,201filed July 13, 1967, and now abandoned.

- BACKGROUND OF THE INVENTION The present invention may be used inconjunction with the defibrillating apparatus disclosed in application,Ser. No. 529,410, filed Feb. 23, 1966, in the name of Joseph H.McLaughlin, now U.S. Pat. No. 3,527,228.

The present invention relates to improved apparatus for treating acardiac patient and more particularly to an improved protector circuitfor preventing stray voltages from affecting the accuracy of the visualrepresentation of the heartbeat produced by an electrocardiograph.

By way of background, multi-purpose electrocardiac apparatus is capableof performing a plurality of functions. One of the functions is tomonitor the heartbeat of a patient and display this heartbeat in visualform on an oscilloscope, graph or the like. This is the conventionalelectrocardiograph apparatus, which obtains its intelligence throughelectrodes applied to the patient. Another function of the improvedelectrocardiac apparatus is to selectively apply defibrillatingcountershock voltage to a patient experiencing fibrillation, which is anirregular heartbeat. Broadly, this consists of applying a very highcountershock voltage to the heart of the patient through electrodesplaced in opposition to each other on the patients back and chest tocause a current flow through the chest cavity. When the countershockvoltage is applied, the patient acts as a conductor and thiscountershock voltage, which may be of extremely high magnitude, on theorder of 7,500 volts, may be transmitted to the electrodes of theelectrocardiograph apparatus and set up stray voltages which maycompletely distort the visual representation of the heartbeat for aperiod of as much as to seconds. It is extremely important that anaccurate visual representation of the patients heartbeat be obtainedimmediately after application of the countershock voltage, so that theeffect of the countershock voltage can be readily observed. The reasonfor this is that many times additional countershock voltage must beapplied immediately after the initial countershock application ofvoltage if the application of the first countershock voltage isineffective. However, as can readily be seen, if the electrocardiographis producing an inaccurate signal, or one which is objectionallydistorted, there is no clear intelligence upon which to base thedecision as to whether additional countershock voltage should beapplied. It is with improved electrocardiac apparatus which overcomesthe foregoing shortcoming that the present invention is concerned.

SUMMARY OF THE INVENTION the patient from adversely affecting the visualrepresentation on the electrocardiograph, thereby providing an accuratepicture of the patients heartbeat at all times regardless of thevoltages to which a patient may be subjected.

A further object of the present invention is to provide improvedelectrocardiograph apparatus including a protector circuit having afirst circuit which causes the display portion of the electrocardiographapparatus to be disconnected from the patient during the application ofa countershock voltage and in addition includes a second circuit whichprevents any countershock voltage applied to the patient from beingtransmitted to the electrocardiograph apparatus in the eventdisconnecting is not fully completed by said first circuit or in theevent the distorting voltage comes from any other source. Other objectsand attendant advantages of the present invention will readily beperceived hereafter.

The improved electrocardiac apparatus of the present invention includesan electrocardiograph for providing a visual representation of thepatients heartbeat and a defibrillator for providing countershockvoltage to the patient for treatment of either ventricular fibrillationor other arrhythmias. The electrocardiograph has electrodes coupled tothe patient in the conventional manner. The defibrillator has electrodescoupled to the chest and back of the patient. A protector circuitinterconnects the defibrillator and the leads leading to theelectrocardiograph display device. When the defibrillator is actuated,the leads to the electrocardiograph are automatically disconnected priorto the application of the countershock voltage and automaticallyreconnected after the countershock voltage has been applied. Thus,during the period of applying the countershock voltage, which is onlyapproximately 2% milliseconds, stray voltages produced incidental to theapplication of defibrillating voltage cannot affect the picture of thepatients heartbeat on the display device. After this brief period ofdisconnection, the picture reappears with complete accuracy. Inaddition, in the event that disconnecting should not be effected asrequired, or in the event the patient is subjected to a stray voltagefrom any source other than the defibrillator, the protector circuitincludes circuit means for preventing such voltages from reaching theapparatus, thereby insuring an accurate picture thereon. By the use ofthe foregoing protector circuit an accurate representation of thepatients heartbeat on the electrocardiograph apparatus is alwaysassured. The present invention will be more fully understood when thefollowing portions of the specification are read in conjunction with theaccompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawing the improvedapparatus is shown which includes an electrocardiograph 10, adefibrillator circuit 11, and a protector circuit 12 coupling theelectrocardiograph and the defibrillator. The electrocardiographapparatus 10 includes three sensor electrodes 13, 14 and 15, the latterbeing coupled to ground. Electrodes l3, l4 and 15 are attached topatient 18, as on his opposite wrists, and suitable electrical contactis made by the use of electrode jelly. Electrode 15 is attached to theleg of the patient. Electrodes l3 and 14 are coupled to protectorcircuit 12 through leads l6 and 17, respectively. Leads 19 and 20,leading from circuit 12, are coupled to amplifier 21 which efiectssuitable amplification of the heartbeat waveform. The amplifiedheartbeat is visually indicated on cathode ray oscilloscope 22 byfeeding the amplified signal from amplifier 21 to vertical amplifier 23through leads 24 and 25, the output of vertical amplifier 23 beingapplied to plates 24 and 25' through leads 26 and 27, respectively. Thissignal is used to modify the trace provided by horizontal free runningsweep amplifier 28 which is coupled to plates 29 and 30 by leads 31 and32, respectively. In lieu of oscilloscope 22 any other type of visualindicating device, such as a graph or an elongated paper tape or thelike, may be used.

The heartbeat waveform comprises a QRS complex including the Q portion,R portion and S portion as shown on the scope in FIG. 1. Thecountershock voltage is applied across the chest cavity of the patientby electrodes 33 and 34 which are coupled to leads 35 and 36,respectively, leading from the defibrillator circuit 11. One of theseelectrodes is mounted on the chest and the other on the back of thepatient 18.

Summarizing the following portion of the specification briefly at thispoint, it can be seen that the electrodes 33 and 34 leading from thedefibrillating circuit 11 and the electrodes 13, 14 and 15 leading tothe electrocardiograph 10 are both mounted on patient 18. Thecountershock voltage, which may be as high as 7,500 volts, or translatedinto energy, in excess of 400 joules, when applied to the patient 18,may also be transmitted through the patient, who thus acts as aconductor, to the electrocardiograph apparatus in the absence of aprotector circuit 12. This direct application to the electrocardiographapparatus will set up stray voltages therein which will completelydistort the picture of the heart waveform on oscilloscope 22 for as longas to seconds. During this period the oscilloscope 22 will be incapableof providing accurate information as to the heartbeat of the patient. Itis during this period that accurate information is critical to determinewhether additional countershock should be applied. The instant protectorcircuit 12 contains switch means which disconnect the electrocardiograph10 from the defibrillator circuit 11 when the countershock voltage isbeing applied and automatically reconnects the electrocardiograph 10 tothe patient 18 after the countershock voltage is no longer beingapplied, to thereby protect the electrocardiograph and insure accuracyof the pictorial representation of the heartbeat thereon. The mode ofoperation of the defibrillator circuit 11 and the interrelationshipbetween the electrocardiograph l0 and the protector circuit 12 will bemore fully understood from the ensuing portions of the description.

The instant defibrillator circuit 11 provides a synchronizedcountershock to a patient, that is, in timed relationship to thepatients heartbeat. This is explained in detail in the above notedcopending application. However, a certain repetition will be made herefor the purpose of completeness. It will be appreciated that theprotector circuit 12 of the present invention can be used with any typeof defibrillator circuit and any type of electrocardiograph.

The amplified heartbeat signal at lead 24 is also fed to Schmitt trigger37 by lead 38 to produce waveform 39 which in turn is fed to single shotmultivibrator 40 by lead 41. It is the multivibrator 40 which produces ausable signal 42 in synchronized relationship to the heartbeat. The leadportion 43 of signal 42 is initiated when the R portion of the heartbeat17 reaches a predetermined magnitude. Lead 45 conducts waveform 42 frommultivibrator 40 to the indicating device 44, which indicates whethermultivibrator 40 is operating satisfactorily. The indicating device 44may include a pulse form inverter (not shown) for inverting waveform 42,an amplifier (not shown) and an integrator (not shown) in series, withthe integrator being coupled to a meter. As is well understood, theforegoing components level out the pulse 42 to provide a constant outputwhich can be read on the meter forming a part of indicating device 44.The foregoing elements are shown in detail in the above mentionedcopending application but are omitted from the instant drawing in theinterest of brevity. The magnitude of the reading on the meterassociated with device 44 is proportional to the heartbeat rate.

When a heart pattern is shown on scope 22 which indicates thatcountershock is necessary, the attending physician will closedefibrillator switch 46 to establish contact between leads 47 and 48.Preferably, however, switch 46 should be in lead 53. The output ofmultivibrator 40 is fed to silicon control rectifier 49 by lead 50,which is connected to lead 45. The silicon control rectifier 49 will beenergized whenever the lead portion 43 of square wave 42 reaches apredetermined magnitude to cause current to flow from B+ to groundthrough lead 51, slow acting relay coil 52, lead 53, silicon controlrectifier 49, lead 47, defibrillation switch 46, and lead 48 to ground.Whenever the silicon control rectifier 49 is energized to complete theabove circuit, relay coil 52 will be energized. At this point it is onlynecessary to understand the energization of coil 52 is synchronized withthe patients heartbeat and that the relay 55 of which coil 52 forms apart actuates the remainder of the circuit which supplies thecountershock voltage.

An AC source 56 is coupled across leads 57 and 58 with sine wave 59depicting the waveform at this point. The normally centered armature 60of switch 61 is selectively movable from a normally open position toeither contact 62 or 63. As can be seen, when armature 60 contactscontact 63, a circuit will be completed through the primary 64 oftransformer 65, which in turn will induce a voltage in the secondarywinding 66. As will become more apparent hereafter, a charge will beplaced on capacitor 67. The magnitude of the charge depends on thelength of time that armature 60 is held on contact 63. After armature 60is released it will return to a normally open position and capacitor 67will retain a charge thereon. If it is desired to cause a lower voltageto be induced on the secondary winding 66, it is merely necessary tomove armature 60 into engagement with contact 62 to complete a circuitto primary winding 64 through resistor 69.

The charge is placed on capacitor 67 through the following circuit. Theoutput of secondary winding 66 is rectified by diodes 70 which arecoupled to one side of secondary 66 by lead 71. Diodes 70 are coupled inseries to prevent a reverse discharge thereacross after a charge isplaced on capacitor 67, which is coupled in series with diodes 70 andsecondary 66 through lead 72, armature 73 of slow acting relay 55, lead74, choke coil 75, lead 76 and lead 77. At this point it is to be notedthat lead 77 is grounded at 82' to the chassis of the apparatus throughresistor 78, armatures 79 and 80 of fast-acting relay and lead 82.

Relay 81 is of the normally open type. Armatures 79 and 80 offast-acting relay 81 are in engagement whenever there is a B+ voltageapplied at terminal 83. The foregoing engagement is effected becausecoil 88 is energized through the path consisting of lead 51, winding 52,lead 53, lead 84, voltage drop resistor 85, lead 86, lead 87, winding 88of relay 81, lead 89 and lead 90 to ground. This energization of relay81 occurs whenever the apparatus is turned on through its master switch(not shown). Otherwise, armatures 79 and 80 are not in engagement andline 77 is not grounded. Because of the parameters of the circuit,armatures 79 and 80 will move into contact to couple the circuit tochassis ground 82'. However, there will be an insufficient flow ofcurrent through slow-acting relay coil 52 to energize slow-acting relay55 and therefore armature 73 thereof will occupy the position shown inthe drawing. There is also a small current flow from lead 86 throughlead 91, diode 92, lead 93, resistor 94 and lead 95 to ground. However,there will be a delay before there is a build-up of voltage acrosscapacitor 96, which is coupled across leads 93 and 95 and it is onlyafter voltage builds up of capacitor 96 that coil 88 will be energized.

The above described voltage which is applied to capacitor 67 isselectively discharged across the chest cavity of a patient to effectdefibrillation. Quantitatively, this voltage may be as high as 7,500volts, or translated into energy, in excess of 400 joules. The magnitudeof this voltage depends upon the charging time through armature 60 andit can be read on meter 97 which is coupled across capacitor 67 throughresistor 98. If for any reason it is desired to harmlessly discharge thevoltage built up on capacitor 67, it is merely necessary to close switch99 to thereby discharge capacitor 67 through resistor 100.

To apply the countershock voltage to the patient 18, electrodes 33 and34, which are in the form of paddles, are coupled onto the opposite ofthe chest cavity of patient 18 by means of a suitable electrode jelly toestablish good electrical contact. One paddle is mounted on the chestand the other paddle is mounted in opposition thereto on the back of thepatient, with the heart essentially being located therebetween. Paddles33 and 34 each include a conducting plate (not shown) which areelectrically connected to leads 35 and 36. The remainder of paddles 33and 34 are made out of a suitable non-conductive plastic material toconfine the electrical countershock. Paddles 33 and 34 are convenientlyprovided with insulating handles 101 and 102.

As noted above, the capacitor 67, which provides the countershockvoltage, is in charged condition while relay armature 73 is in theposition shown in the drawing. In order to cause capacitor 67 todischarge across paddles or electrodes 33 and 34, armature 73 ofslow-acting relay 55 must move from contact 103 to contact 104. However,in the absence of opening the connection to chassis ground 82' throughlead 82 before armature 73 engages contact 104, there is the possibilitythat a person in contact with the patient 18 mayform a leg of thecircuit and thus receive an electrical shock. This would occur if hewere grounded and touching either the patient or anything in electricalcontact with him while the shock was being administered.

At this point it is to be noted that slow-acting relay 55 is a highvoltage vacuum relay wherein armature 73 and contacts 103 and 104 areencased in a vacuum envelope (not shown) and coil 52 is mounted inencircling relationship to the envelope. This type of relay must be usedto prevent arcing during the switching action. Fast acting relay 81 isalso a high voltage vacuum relay of the type having armatures 79 and 80within a vacuum envelope 105 and a relay coil 88 surrounding theenvelope.

In operation, the person administering the countershock closes switch 46when he determines that countershock is necessary, as indicated by thepicture of the heartbeat on oscilloscope 22. Upon the closing of switch46, both sides of fast-acting relay coil 88 will be grounded, one sidethrough leads 89 and 90, and the other side through leads 87 and 86,resistor 85, lead 84, silicon control rectifier 49, lead 47, switch 46and lead 48. This grounding will occur only when silicon controlrectifier 49 is conducting and it does so only when the proper voltageis supplied thereto from the single shot multivibrator 40 through lead50. In other words, the silicon control rectifier 49 will conduct atportion 43 of waveform 42 produced by multivibrator 40. This occurs atthe R portion of the heartbeat. It is approximately 2 milliseconds afterthis that armatures 79 and 80 of relay 81 will separate and this willdisconnect the circuit from chassis ground. The foregoing is explainedin greater detail in the above mentioned copending application.

Contact between armatures 79 and 80 must be broken to disconnect thecircuit from chassis ground 82 before armature 73 of slow-acting relay55 reaches contact 104 to thereby insure that the attendant cannot besubjected to the coun tershock voltage. Slow-acting relay 55 requiresapproximately milliseconds for armature 73 to reach contact 104 afterleaving contact 103. When armature 73 reaches contact 104, capacitor 67,which has countershock voltage stored thereon, will discharge throughchoke coil 75, armature 73 and leads 36 and 35, across paddles orelectrodes 33 and 34, thereby establishing an electric discharge throughthe chest of the patient. The choke coil 75 causes the discharge toextend over a period of approximately 2% milliseconds (0.0025 seconds).The countershock voltage will be synchronized with the heartbeat andfall between the R and S waves.

The armature 73 will remain in engagement with contact 104 for as longas defibrillation switch 46 is held closed after contact is once madebecause once the silicon control rectifier 49 has been triggered bywaveform 42, it will continue to con duct. Capacitor 67 provides only asingle discharge each time switch 46 is closed. In other words, theattendant may maintain the defibrillation switch 50 closed for as longas he desires but he will get only a single shot of countershockvoltage. Another shot can be obtained only after the capacitor 67 isagain charged up in the manner described in detail above, and afterswitch 46 is again closed. After switch 46 has been released, it returnsto a normally open position. The armature 73 of slow-acting relay 52will move from contact 104 to contact 103 in a time period dependent onthe inherent delay in the relay 55. This occurs because the opening ofswitch 46 terminates the flow of current through slow-acting relay coil52.

However, armatures 79 and 80 of fast-acting relay 81 do not return intocontact with each other before armature 73 leaves contact 104, to insurethat an undesired countershock cannot be applied to either the patientor the attendant through ground. The circuit containing capacitor 96achieves this function. More specifically, after both sides offast-acting relay coil 88 were grounded by switch 46 incidental toinitiating countershock, capacitor 96 is also discharged across resistor94. However, after switch 46 is opened, relay coil 88 will not beenergized until after capacitor 96 becomes energized and this takes aperiod of time depending on the time constant of the circuit consistingof capacitor 96 and resistor 94. The armature 73 of slow-acting relay 55returns to contact 103 and it takes a period of time which is dependenton the inherent delay in the relay for this switching action to becompleted. However, the switching action effected by fast-acting relay81 is not completed until a time greater than 20 milliseconds because ofthe action of capacitor 96. This insures that the fast-acting relay 81will not close until after the armature 73 of slow-acting relay 55 is nolonger in contact with contact 104.

As noted above, when the countershock voltage is applied to the patient18, he can act as a conductor to transmit this voltage to theelectrocardiograph apparatus 10 and this would normally distort thepicture on the scope 22 for a period of as much as 20 or 30 seconds,during which time it is important that the physician be able to monitorthe patients heartbeat accurately. In certain cases the foregoingvoltage can permanently damage apparatus 10. In accordance with thepresent invention, a protector circuit 12 is supplied for preventing theforegoing by producing a selective switching action. More specifically,a reed relay 106 is provided having a glass envelope 107 containingarmatures 108 and 109, and a coil 110. Envelope 107 is evacuated toprevent arcing between leads 108 and 109 as they open and close. Coil110 is energized from a 13+ source through lead 1 11, voltage dropresistor 112, lead 1 13 and lead 114, which is coupled to ground. Inaddition, a reed relay is provided having armatures 116 and 117 in glassenvelope 118 and a coil 119 wound around envelope 118. Coil 119 iscoupled to the B+ source also through leads 111, 112, 113, 120 and 121to ground. it is to be noted that whenever the B+ source connected tolead 111 is energized, that is, when the machine is connected to anelectrical source and its master switch (not shown) is on, relay coils110 and 119 will be energized to cause the respective armatures in theenvelopes associated therewith to be in contact to thereby permit theamplifier 21 to be connected to electrodes 13 and 14. It will beappreciated that a single coil can be used around envelopes 107 and 111instead of two coils 1 10 and 1 19.

Whenever defibrillator switch 46 is closed, transistor 122 will couplelead 113 to ground through leads 123 and 124. Both sides of relay coils110 and 119 will thus be grounded when transistor 122 conducts, and itconducts only when defibrillator switch 46 is closed and there is acurrent flow from lead 48 to transistor 122 through lead 125. Reedrelays 106 and 115 are of the fast-acting type which will opensubstantially simultaneously with the energization of fast-acting relay81 to thereby insure that the leads to amplifier 21 are open before thecountershock voltage is applied, that is, before armature 73 ofslow-acting relay 55 engages contact 104. Relays 106 and 115 will closeonly after defibrillator switch 46 is released and returns to an openposition shown in the drawing whereupon transistor 122 will cease toconduct. At this time the countershock voltage has already been appliedto the patient and there is no danger of such voltage being applied toamplifier 21.

A neon lamp is associated with each of leads l6 and 17. Morespecifically, neon lamp 126 is coupled to lead 16 by lead 127 and saidlamp in turn is coupled to ground by lead 128. In addition, a neon lamp129 is connected between lead 17 and ground through leads 130 and 131.In the event that the voltage applied across leads 16 and 17 exceeds apredetermined value, for example, 50 volts, neon lamps 126 and 129 willconduct this voltage to ground while relays 106 and 115 are open. Thisprevents any residual voltage across leads 16 and 17 from being appliedto electrocardiograph 10 after relays 106 and 1 15 are reclosed.

There may also be times when leads 16 and 17 are subjected to strayvoltages when defibrillation is not being effected. Under thesecircumstances, relays 106 and 1 15 will be closed. If these strayvoltages exceed a predetermined voltage, neon lamps 126 and 129 willconduct to ground, thereby preventing distortion of the picture onoscilloscope 22 or danger to amplifier 21. Lamps 126 and 129 willcontinue to conduct until such time as the voltage applied to leads 16and 17 is below a certain value, at which time they will cease toconduct and leads l6 and 17, relays 106 and 115, and leads 19 and 20will thereafter conduct normally to the amplifier 21.

It can thus be seen that an extremely simple protector circuit has beenapplied to electrocardiac apparatus, consisting of an electrocardiographand a defibrillator circuit, for preventing countershock voltagesapplied to the patient from adversely affecting the electrocardiographby either damaging the amplifier or distorting the visual representationof the heartbeat on the oscilloscope. In addition, the protector circuitincludes an arrangement for preventing stray voltages which are notnecessarily originated by the defibrillator from adversely affecting theelectrocardiograph in the same manner. It will be appreciated thatprotector circuit 12 may be used with anytype of electrocardiograph andany type of defibrillator or other electronic apparatus used in thetreatment of a cardiac patient.

I claim:

1. An electrocardiograph circuit comprising electrode means adapted tobe coupled to a patient for detecting a heartbeat, heartbeat signalamplifier means, display means for providing a visual indication of saidpatients heartbeat, circuit means coupling said electrode means and saidheartbeat signal amplifier means and said display means, circuitprotector means in said circuit means coupled between said electrodemeans and said heartbeat signal amplifier means for effectivelydisconnecting said electrode means from said heartbeat signal amplifiermeans for selectively preventing distortion producing voltages frombeing conducted to said heartbeat signal amplifier means and therebypreventing distortions in said heartbeat signal amplifier means whichcan result in a distorted representation on said display means, saidcircuit protector means including relay means, defibrillator circuitmeans, switch means in said defibrillator circuit means for selectivelyenergizing said defibrillator circuit means to apply a countershockvoltage to a patient, second circuit means coupling said defibrillatorcircuit means to said circuit protector means and energizable incidentalto the energization of said defibrillator circuit means for causing saidcircuit protector means to prevent distortion producing voltagesproduced incidental to defibrillation from being conducted to saidheartbeat signal amplifier means, and third circuit means having voltagedischarge means therein coupled between said electrode means and saidrelay means for conducting voltages in excess of a predetermined valueapplied to said electrode means away from said relay means and saidheartbeat signal amplifier means, said relay means comprising fastacting reed relay means in said circuit means for opening said circuitmeans between said electrode means and said heartbeat signal amplifiermeans before said defibrillator circuit means apply said countershockvoltage to said patient.

2. An electrocardiograph circuit comprising electrode means adapted tobe coupled to a patient for detecting a heartbeat, heartbeat signalamplifier means in said electrocardiograph circuit for amplifying aheartbeat signal picked up by said electrode means, display means forproviding a visual indication of said patients heartbeat, first circuitmeans coupling said electrode means and said heartbeat signal amplifiermeans, second circuit means coupling said amplifier means and saiddisplay means, circuit protector means in said first circuit meanscoupled between said electrode means and said heartbeat signal amplifiermeans with said electrode means being in immediate precedingrelationship to said circuit protector means which in turn are inimmediate preceding relationship to said heartbeat amplifier means, saidcircuit protector means effectively disconnecting said electrode meansfrom said heartbeat signal amplifier means for preventing distortionproducing voltages from being conducted to any portion of said heartbeatsignal amplifier means and thereby preventing distortions in saidheartbeat signal amplifier means which can result in a distortedrepresentation on said display means, said circuit protector meansincluding relay means for disconnecting said electrode means from saidheartbeat signal amplifier means, defibrillator circuit means, switchmeans in said defibrillator circuit means for selectively energizingsaid defibrillator circuit means to apply a countershock voltage to apatient, third circuit means coupling said defibrillator circuit meansto said circuit protector means and energizable incidental to theenergization of said defibrillator circuit means for causing saidcircuit protector means to prevent distortion producing voltagesproduced incidental to defibrillation from being conducted to saidheartbeat signal amplifier means, means for causing said circuitprotector means to automatically reconnect said electrode means to saidheartbeat signal amplifier means after said switch means is releasedafier the termination of said countershock voltage to cause said displaymeans to provide said visual indication of said patient s heartbeatimmediately after the termination of said countershock voltage, saidrelay means comprising fast acting reed relay means in said firstcircuit means for opening said first circuit means between saidelectrode means and said heartbeat signal amplifier means before saiddefibrillator circuit means apply said countershock voltage to saidpatient.

3. An electrocardiograph circuit comprising electrode means adapted tobe coupled to a patient for detecting a heartbeat, heartbeat signalamplifier means in said electrocardiograph circuit for amplifying aheartbeat signal picked up by said electrode means, display means forproviding a visual indication of said patients heartbeat, first circuitmeans coupling said electrode means and said heartbeat signal amplifiermeans, second circuit means coupling said amplifier means and saiddisplay means, circuit protector means in said first circuit meanscoupled between said electrode means and said heartbeat signal amplifiermeans with said electrode means being in immediate precedingrelationship to said circuit protector means which in turn are inimmediate preceding relationship to said heartbeat amplifier means, saidcircuit protector means effectively disconnecting said electrode meansfrom said heartbeat signal amplifier means for preventing distortionproducing voltages from being conducted to any portion of said heartbeatsignal amplifier means and thereby preventing distortions in saidheartbeat signal amplifier means which can result in a distortedrepresentation on said display means, said circuit protector meansincluding relay means for disconnecting said electrode means from saidheartbeat signal amplifier means, defibrillator circuit means, switchmeans in said defibrillator circuit means for selectively energizingsaid defibrillator circuit means to apply a countershock voltage to apatient, third circuit means coupling said defibrillator circuit meansto said circuit protector means and energizable incidental to theenergization of said defibrillator circuit means for causing saidcircuit protector means to prevent distortion producing voltagesproduced incidental to defibrillation from being conducted to saidheartbeat signal amplifier means, and a fourth circuit means havingvoltage discharge means therein coupled between said electrode means andsaid relay means for conducting voltages in excess of a predeterminedvalue applied to said electrode means away from said relay means andsaid heartbeat signal amplifier means, means for causing said circuitprotector means to automatically reconnect said electrode means to saidheartbeat signal amplifier means after said switch means is releasedafter the termination of said countershock voltage to cause said displaymeans to provide said visual indication of said patients heartbeatimmediately after the termination of said countershock voltage, saidrelay means comprising fast acting reed relay means in said firstcircuit means for opening said circuit means between said electrodemeans and said heartbeat signal amplifier means before saiddefibrillator circuit means apply said countershock voltage to saidpatient.

1. An electrocardiograph circuit comprising electrode means adapted tobe coupled to a patient for detecting a heartbeat, heartbeat signalamplifier means, display means for providing a visual indication of saidpatient''s heartbeat, circuit means coupling said electrode means andsaid heartbeat signal amplifier means and said display means, circuitprotector means in said circuit means coupled between said electrodemeans and said heartbeat signal amplifier means for effectivelydisconnecting said electrode means from said heartbeat signal amplifiermeans for selectively preventing distortion producing voltages frombeing conducted to said heartbeat signal amplifier means and therebypreventing distortions in said heartbeat signal amplifier means whichcan result in a distorted representation on said display means, saidcircuit protector means including relay means, defibrillator circuitmeans, switch means in said defibrillator circuit means for selectivelyenergizing said defibrillator circuit means to apply a countershockvoltage to a patient, second circuit means coupling said defibrillatorcircuit means to said circuit protector means and energizable incidentalto the energization of said defibrillator circuit means for causing saidcircuit protector means to prevent distortion producing voltagesproduced incidental to defibrillation from being conducted to saidheartbeat signal amplifier means, and third circuit means having voltagedischarge means therein coupled between said electrode means and saidrelay means for conducting voltages in excess of a predetermined valueapplied to said electrode means away from said relay means and saidheartbeat signal amplifier means, said relay means comprising fastacting reed relay means in said circuit means for opening said circuitmeans between said electrode means and said heartbeat signal amplifiermeans before said defibrillator circuit means apply said countershockvoltage to said patient.
 2. An electrocardiograph circuit comprisingelectrode means adapted to be coupled to a patient for detecting aheartbeat, heartbeat signal amplifier means in said electrocardiographcircuit for amplifying a heartbeat signal picked up by said electrodemeans, display means for providing a visual indication of saidpatient''s heartbeat, first circuit means coupling said electrode meansand said heartbeat signal amplifier means, second circuit means couplingsaid amplifier means and said display means, circuit protector means insaid first circuit means coupled between said electrode means and saidheartbeat signal amplifier means with said electrode means being inimmediate preceding relationship to said circuit protector means whichin turn are in immediate preceding relationship to said heartbeatamplifier means, said circuit protector means effectively disconnectingsaid electrode means from said heartbeat signal amplifier means forpreventing distortion producing voltages from being conducted to anyportion of said heartbeat signal amplifier means and thereby preventingdistortions in said heartbeat signal amplifier means which can result ina distorted representation on said display means, said circuit protectormeans including relay means for disconnecting said electrode means fromsaid heartbeat signal amplifier means, defibrillator circuit means,switch means in said defibrillator circuit means for selectivelyenergizing said defibrillator circuit means to apply a countershockvoltage to a patient, third circuit means coupling said defibrillatorcircuit means to said circuit protector means and energizable incidentalto the energization of said defibrillator circuit means for causing saidcircuit protector means to prevent distortion prOducing voltagesproduced incidental to defibrillation from being conducted to saidheartbeat signal amplifier means, means for causing said circuitprotector means to automatically reconnect said electrode means to saidheartbeat signal amplifier means after said switch means is releasedafter the termination of said countershock voltage to cause said displaymeans to provide said visual indication of said patient''s heartbeatimmediately after the termination of said countershock voltage, saidrelay means comprising fast acting reed relay means in said firstcircuit means for opening said first circuit means between saidelectrode means and said heartbeat signal amplifier means before saiddefibrillator circuit means apply said countershock voltage to saidpatient.
 3. An electrocardiograph circuit comprising electrode meansadapted to be coupled to a patient for detecting a heartbeat, heartbeatsignal amplifier means in said electrocardiograph circuit for amplifyinga heartbeat signal picked up by said electrode means, display means forproviding a visual indication of said patient''s heartbeat, firstcircuit means coupling said electrode means and said heartbeat signalamplifier means, second circuit means coupling said amplifier means andsaid display means, circuit protector means in said first circuit meanscoupled between said electrode means and said heartbeat signal amplifiermeans with said electrode means being in immediate precedingrelationship to said circuit protector means which in turn are inimmediate preceding relationship to said heartbeat amplifier means, saidcircuit protector means effectively disconnecting said electrode meansfrom said heartbeat signal amplifier means for preventing distortionproducing voltages from being conducted to any portion of said heartbeatsignal amplifier means and thereby preventing distortions in saidheartbeat signal amplifier means which can result in a distortedrepresentation on said display means, said circuit protector meansincluding relay means for disconnecting said electrode means from saidheartbeat signal amplifier means, defibrillator circuit means, switchmeans in said defibrillator circuit means for selectively energizingsaid defibrillator circuit means to apply a countershock voltage to apatient, third circuit means coupling said defibrillator circuit meansto said circuit protector means and energizable incidental to theenergization of said defibrillator circuit means for causing saidcircuit protector means to prevent distortion producing voltagesproduced incidental to defibrillation from being conducted to saidheartbeat signal amplifier means, and a fourth circuit means havingvoltage discharge means therein coupled between said electrode means andsaid relay means for conducting voltages in excess of a predeterminedvalue applied to said electrode means away from said relay means andsaid heartbeat signal amplifier means, means for causing said circuitprotector means to automatically reconnect said electrode means to saidheartbeat signal amplifier means after said switch means is releasedafter the termination of said countershock voltage to cause said displaymeans to provide said visual indication of said patient''s heartbeatimmediately after the termination of said countershock voltage, saidrelay means comprising fast acting reed relay means in said firstcircuit means for opening said circuit means between said electrodemeans and said heartbeat signal amplifier means before saiddefibrillator circuit means apply said countershock voltage to saidpatient.